1. Field of the Invention
This invention relates to an optical multilayer reflective film having a feature that it selectively reflects light with a particular wavelength. Further, the present invention relates to a process for orderly aligning metal particles, and in particular relates to a process for aligning metal particles in a layer in a polymer film in parallel with the film.
2. Description of the Background Art
Optical communication has become essential as technique supporting large-capacity communication as internet has been rapidly prevailed. Furthermore, prevalence of high-density multiple-wavelength communication has increased the number of wavelengths used, leading to drastic increase of the number of optical components used. Among these, optical elements employing a reflective/transmitting optical multilayer film with wavelength selectivity has become essential components.
Conventionally, multilayer dielectric optical films have been frequently used as a functional film controlling reflection properties at a particular wavelength of light. These dielectric multilayer films are generally composed of alternatively layered high-refractive-index layers and low-refractive-index layers which are optically substantially transparent at a particular wavelength on a substrate surface. Specifically, metal oxide and/or fluoride layers such as Ta2O5, TiO2, SiO2 and MgF2 are formed in a multilayer structure so as to utilize interference between reflecting light and transmitted light in their interface, whereby optical properties such as transmission and reflection is achieved.
However, for preparing a multilayer dielectric optical film having such properties, it is necessary to, after selecting materials to be used and determining a layer structure with multiple layers, conduct film deposition while highly precisely controlling a thickness and a refractive index of each layer. In particular, advanced film-deposition technique is required for preparing a reflecting film which can selectively reflect light with a significantly narrow half width, resulting in increase in manufacturing steps and tendency to a higher manufacturing cost.
Patent References 1 to 4 have described a multilayer-film reflecting mirror having layered metal films, which is a reflecting mirror for a wavelength within in a X-ray range and additionally is a layered of high-and low-refractive-index layers to a wavelength within in a X-ray range. The principle is the same as that in the above-mentioned optical dielectric multilayer film.
With respect to organic/inorganic composite materials, there have been many studies on them. Organic/inorganic composite materials in which inorganic materials are complexed with organic polymers have been intensely developed because they allow for modification of functional properties of a polymer. Among others, studies have been intensely conducted, on a process for dispersing metal particles in a polymer with a certain regularity. For example, there has been described that a metal complex as a precursor for metal particles is sublimed and becomes contact with a block copolymer having different abilities of metal reduction under nitrogen, whereby the complex is selectively reduced only in one phase to achieve nano-level alignment of metal particles (see, for example, Non-patent Reference Nos. 1 to 3).
However, in terms of reported metal particle alignment in the polymer, distribution of each polymer in a co-polymer (alignment style) is determined in a self-organized manner, and there have been no reports in which metal particle alignment is completely controlled. In particular, there are no known methods for aligning metal particles in a layer in a polymer film in parallel with the film.